Crystallizations of Novel Forms of Alcohol Dehydrogenase

Abstract

Alcohol dehydrogenases in nature are derived from different protein families (cf Jörnvall et al., 1993). The mammalian alcohol dehydrogenases constitute what presently appears to be six classes within a large family of medium-chain dehydrogenases and reductases, MDR, with at least seven characterized activity types (Persson et al., 1994). The classes of the mammalian alcohol dehydrogenases differ in structure (55–68% sequence identity), substrate pockets, subunit interactions, and other properties. Much of these aspects has been interpreted by comparisons and modelling studies based on crystallographic analyses of just two of the enzymes of one class, the class I horse (Eklund et al., 1976) and human (Hurley et al., 1991) enzymes, constituting the classical liver enzyme with ethanol activity. It is desirable to get direct crystallographic data on the conformations of more of the enzymes, especially since differences exist between the classes, class-hybrid properties have been found in early enzyme forms (of fish), and the two well-characterized classes, I and III, differ in internal variability patterns (Danielsson et al., 1994a). We have therefore crystallized five novel forms of these dehydrogenases, which should enable further structural characterizations and hence evaluation of the conclusions from modelling and from natural variants.